Tag: vomitoxin

Managing and Scouting Fields for Fusarium Head Blight

Alyssa Koehler, Extension Field Crop Pathologist | akoehler@udel.edu
University of Delaware

Wheat anthesis (flowering) is underway and will be continuing for the next 1-2 weeks across the region. Up until the rains this past weekend, we have been at low FHB risk. We are currently tracking as medium-high risk for very susceptible varieties and low-medium risk for varieties with some level of resistance (Figure 1). If you are planning for wheat fungicide application, scout frequently, looking for yellow anthers in the center of the wheat head (Figure 2) to signal that flowering has begun (Feekes 10.5.1). Depending on the weather, we can usually expect flowers to start showing up on wheat heads 3-5 days after full head emergence, with cool weather this can stretch this process out to 7-10 days. Anthers can remain attached after flowering, but become a pale white. For best mycotoxin (DON) control, it is better to be at flowering or a few days beyond than to spray too early when heads are not out yet (especially those secondary tillers). Fungicide products should be applied at the manufacturers recommended rate with nozzles angled 30-45° from horizontal (30 degrees is better than 45). Nozzles angled both forward and backward or twinjet nozzles that spray in two directions give better contact with the head and increase fungicide efficacy. For ground sprays, fungicides should be applied in at least 10-15 gallons of water per acre; aerial applications are recommended at 5 gallons per acre.

Figure 1. FHB Risk Model for very susceptible (top) and susceptible varieties (bottom) May 3, 2023 (wheatscab.psu.edu).
Figure 2. Wheat at flowering (Feekes 10.5.1) with yellow anthers visible 3-4 days after heads emerge.

Once wheat has flowered, symptoms of FHB are usually visible in 18-24 days, but cool weather can slow symptom development. Heads with FHB will have bleached florets or bleached sections of the head and may have pink growth on spikelets. Glume blotch may also be present, but typically has more of a grey appearance. You can follow these steps to assess the severity of FHB present in your field.

  1. For every 10 acres of field, randomly select one spot to survey.
  2. Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to look at on the plant or detach and place into a bag. (Looking down may bias the heads you select).
  3. Once you have randomly collected the heads, rate the percent of each head with symptoms of FHB (bleaching or pink growth on spikelets). You can use the scale below to help calibrate your eye (next page).
  4. After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected. (Ex. You rate 10 heads with severity values: 0%, 10%, 30%, 0%, 0%, 20%, 10%, 0%, 0%, 0%. These add up to 70. 70/10 heads = 7% overall FHB severity). Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight. It is possible to have delayed or lower levels of symptoms and still have DON.
  5. Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvested as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested. 

2021 Maryland Small Grain Variety Trials

Results from the University of Maryland Small Grain Variety Trials are in the tables below. To download a pdf copy of the report, click here or visit https://psla.umd.edu/extension/md-crops/small-grains-maryland.

For questions regarding the small grain trials, contact Dr. Vijay Tiwari (vktiwari@umd.edu) or Dr. Nidhi Rawat (nidhirwt@umd.edu).

If you’d like to learn more about how to interpret variety trial data, view our fact sheet by clicking here.

Click to Download The 2021 Small Grain Variety Trials

 

 

Wheat Variety Selections—An Important Factor For Managing Head Blight

Andrew Kness, Agriculture Agent
University of Maryland Extension, Harford County

Compared to the 2018 wheat crop, 2019 was a much better year for Fusarium head blight (FHB, also known as head scab). Growing quality wheat in Maryland starts with proper variety selection. As you look ahead to the 2020 wheat crop, select wheat varieties that have good FHB ratings. There are no varieties with complete resistance to head scab; only varying degrees of susceptibility. Nevertheless, planting a somewhat resistant variety will go a long way in managing FHB and keeping vomitoxin levels (DON) lower in your grain compared to a susceptible variety.

To aid in your selection of wheat varieties, the University of Maryland screens several wheat varieties for their resistance to Fusarium graminearim, the causal agent of FHB. The results from the 2019 trials can be found here.

Additional considerations for FHB management include:

  • Planting behind soybeans rather than corn or other small grains. The FHB pathogen survives on residue of corn, wheat, barley, oats, and other grasses; however, it does not persist on soybean residue.
  • If planting into corn residue, consider tillage if it is an option for your farm. Sizing and burying corn residue will accelerate its decomposition and reduce the FHB pathogen survival.
  • Fungicides in spring 2020. Please note that fall fungicide applications do not have any effect on managing FHB. More information will be covered concerning fungicide recommendations in the spring, or read this article from earlier this year.